Seating depth vs velocity - who is right?

[lrgoodger]

In Mike Ratigan's book Extreme Rifle Accuracy on page 128, it says;

"...found conclusively that changes in bullet seating depth had no significant effect on pressure or velocity."

In the Accurate Shooter review of quickload at

http://www.accurateshooter.com/gear-reviews/test-quickload-review/

under Bullet Seating Depth it says;

"If you haven’t tried QuickLOAD, you may be surprised at how much of an effect relatively small changes in seating depth can have. QuickLOAD gives you a good sense of how seating depth (and case capacity) affects load pressure."

Are these two statements at odds with each other or am I missing something?

 

[Dusty Stevens]

Mike ratigan has put more rounds downrange than the programmer of quickload. Altho if he has ever used a chronograph he is one of the 1/2% of br shooters that ever have. But with his experience he knows pressure without a chrony. We BR shooters only care about whats on the paper.

 

[savagedasher]

I find QL to be correct . With small cases like a Dasher. I have found cases with different H20 capacity shoot over 10FPS in speed. .02 in H20 capacity is the same as .01 of powder in bullet speed. in a Dasher. I have a few cases that I have checked . The total case weight the same but the internal H20 capacity is one full GR different And 12 Fps.. If you want to lower your ES Sort your cases With bullet speed or H20 capacity. Better yet do both. Larry

 

[CharlieNC]

I have chronoed several seating depth trials and all had consistent velocity increase as length was reduced; not large changes but consistent. You can't fool the physics.

 

[jimcasey01]

In Mike Ratigan's book Extreme Rifle Accuracy on page 128, it says;

"...found conclusively that changes in bullet seating depth had no significant effect on pressure or velocity."

In the Accurate Shooter review of quickload at

http://www.accurateshooter.com/gear-reviews/test-quickload-review/

under Bullet Seating Depth it says;


"If you haven’t tried QuickLOAD, you may be surprised at how much of an effect relatively small changes in seating depth can have. QuickLOAD gives you a good sense of how seating depth (and case capacity) affects load pressure."

Are these two statements at odds with each other or am I missing something?

If it is really that important for you to know, why not do a very simple test. That will give you a much more accurate answer than the 50 posts of opinion that are to follow.

It appears to me that there are 3 types of reloaders on this and all forums.
1) Those who want the best accuracy, and get 100% of their information from the printed page or screen, blindly accepting the printed word as gospel. God for bid that there could be info put out there that is not correct.
2) Those that want the best accuracy, but never investigate any new ideas, and will never make any changes, ‘cause it works as is. (Goes bang)
3) Those that want the best accuracy, and get their info from as many sources as they can (that they deem reliable), as in #1, but also continue to test, trying to verify info gleaned from outside sources is accurate, and to improve on their current status. Good enough is never a place to stop testing for them.

 

[Mozella]

I guess it depends on what you think "significant" or "no effect" means. Here's a graph of some recent seating tests i did with my 6mm BR Norma rifle with three different bullets. I shot a five shot group at each of the seating depths.

The Barnes Match Burner 105gr bullets show a change of 23fps between a jump of .020" and just contacting the lands.

The Sierra Match King 107gr bullets show a 38fps change between a jump of .015" and seated .015" into the lands.

The Berger VLD 95 grain bullets showed the least variation.

Although I don't notice what I would consider a lot of muzzle velocity variance with seating depth, I find a definite effect on group size and while a jump of .005" works well for many of my .223 Rem and 6mm BR Normal loads, some recipes prefer a greater jump and some prefer to be seated into the lands for best accuracy.
MV vs Seating Depth

 

[Webster]

No disrespect to Mike Ratigan but I can see him measuring fps but do you really think he had a pressure sensor on the barrel and a high speed oscilloscope to measure pressure.

 

[lrgoodger]

I guess it depends on what you think "significant" or "no effect" means.

That was my best guess as well. Something that may not be significant at 100 yards could be very significant at 1000.

Physics says with a fixed powder load, pressure and therefore velocity will vary directly with case volume. Case volume increases with seating the bullet out, however slightly. How significant is it is the right answer.

Thanks guys.

 

[stansrifles]

I have a question about quick load is this a program that cost the shooters money to by or is it free program.
Stan

 

[memilanuk]

$153

 

[stansrifles]

I should have known that my bad.
Stan

 

[Alex Wheeler]

My experience is, there is very little change in velocity and/or pressure from In the Lands -to- Off the Lands.
There also is very little change to POI on the targets, which physically proves the lack of increased velocity from In to Off.


Below is a seating depth test:

Notice the change in vertical dispersion (ES) between each group, but how little over all change to the POI heights.
Which shows well how little the total velocity spread was effected by seating.


Below is a 450-yard seating test: notice with this one, as the seating was moved away (Off) the POI to each group slightly rose.
Hence the velocity increased linearly Off the rifling, do to increased load density of this specific load combination of a high starting density.

My 2-cents
Donovan

Are those the same loads at both yardages? Interesting how the best at 450 was not the best at 1k

 

[Joe R]

LRGoodger said:

Seating depth vs velocity - who is right?

In Mike Ratigan's book Extreme Rifle Accuracy on page 128, it says;

"...found conclusively that changes in bullet seating depth had no significant effect on pressure or velocity."

In the Accurate Shooter review of quickload at

http://www.accurateshooter.com/gear-reviews/test-quickload-review/

under Bullet Seating Depth it says;

"If you haven’t tried QuickLOAD, you may be surprised at how much of an effect relatively small changes in seating depth can have. QuickLOAD gives you a good sense of how seating depth (and case capacity) affects load pressure."

Are these two statements at odds with each other or am I missing something?

LRGoodger, this is really a good question, thanks for asking it.

Having to choose between QuickLoad and Mike Rattigan's opinion is fundamentally a choice between physics or one man's opinion based on personal observations and analysis (Yes, I know that QL is a model of physics and doesn't account for all the variables in the real world). Given that choice it's a no-brainer on which to pick.

savagedasher said:

I find QL to be correct . With small cases like a Dasher. I have found cases with different H20 capacity shoot over 10FPS in speed. .02 in H20 capacity is the same as .01 of powder in bullet speed. in a Dasher. I have a few cases that I have checked . The total case weight the same but the internal H20 capacity is one full GR different And 12 Fps.. If you want to lower your ES Sort your cases With bullet speed or H20 capacity. Better yet do both. Larry

Larry,
That is really good info to have and I really appreciate you sharing it. I have found that the more variables I nail down the better shooter I become. Case capacity is my last variable that I can nail down. You have essentially confirmed what I have suspected for some time, but have been too lazy to explore.

I was planning on measuring case volume in the next few days and putting it to a test. However, I have found water to be too unreliable a measure because of the variability of tension (yes, I have used alcohol). I have considered using ball powder as a measuring medium (as Donovan has suggested in the past), but I have decided against it because the medium itself is variable. So I've decided to use the common household fine salt that you can find in most grocery stores for 60 cents a pound. That should make it pretty consistent and repeatable and I won't have to dry the cases afterwards.

Right now my five shot groups SD's are consistently at 5 or slightly better. A couple of times I 've had SDs of 1. My ES are consistently at 12 fps or less. I know I can do better.

Kindest regards,

Joe

 

[memilanuk]

I find QL to be correct . With small cases like a Dasher. I have found cases with different H20 capacity shoot over 10FPS in speed. .02 in H20 capacity is the same as .01 of powder in bullet speed. in a Dasher. I have a few cases that I have checked . The total case weight the same but the internal H20 capacity is one full GR different And 12 Fps.. If you want to lower your ES Sort your cases With bullet speed or H20 capacity. Better yet do both.

Am I the only one wondering if maybe there was a decimal point slipped in there somewhere... like 0.02 gn of H20 capacity is the same as 0.01gn of powder in terms of velocity, but then there's talk of a full *grain* equalling 12 fps...?

 

[Joe R]

memilanuk said:

Am I the only one wondering if maybe there was a decimal point slipped in there somewhere... like 0.02 gn of H20 capacity is the same as 0.01gn of powder in terms of velocity, but then there's talk of a full *grain* equalling 12 fps...?

memilanuk,

I don't know have or know much about the dashers, but in my .308, at the velocity I am getting, a 0.1 grain equals 4-5 fps change. A full grain would blow primers.

Joe

 

[memilanuk]

Kinda my point... but I think it also depends somewhat on where you are on the load line. It's been demonstrated time and again that there can be nodes or 'plateaus' where the change in fps for a given charge increment decreases.

 

[daniel brothers]

Quote...

Regardless, at times what I see from fine tuning at 450yds does not hold up at 1000yds.



Why not?

 

[savagedasher]

I find QL to be correct . With small cases like a Dasher. I have found cases with different H20 capacity shoot over 10FPS in speed. .02 in H20 capacity is the same as .01 of powder in bullet speed. in a Dasher. I have a few cases that I have checked . The total case weight the same but the internal H20 capacity is one full GR different And 12 Fps.. If you want to lower your ES Sort your cases With bullet speed or H20 capacity. Better yet do both.

Am I the only one wondering if maybe there was a decimal point slipped in there somewhere... like 0.02 gn of H20 capacity is the same as 0.01gn of powder in terms of velocity, but then there's talk of a full *grain* equalling 12 fps...?

It is Based on the Case volume to start with. And bore size. The smaller the bore the bigger the pressure difference The larger the case capacity the less pressure change .01 tenth makes.. Simple Math
Larry

 

[savagedasher]

Quote...

Regardless, at times what I see from fine tuning at 450yds does not hold up at 1000yds.



Why not?

Driver error an conditions. ;D ;D Why cant YOU make the group size get smaller then the second shot with more shots. That being said why shoot more then two shots when tuning. ;D I like 2 shots when tuning 3 or 5 is a bad number the way I tune. Two' two shot targets is better then 3 3 -two shot targets are better then 5. With two shot you take the total amount of group size and divide the number of two shot into the total. I know I can shoot two shots in near the same conditions them I can more. The target wont be a wall hanger or a pocket piece. But I'm not tune for that. ;D Larry

 

[Alex Wheeler]

Donovan, your full of it! I have tuned at 100 yards and can hit gongs at 1k, SO THERE! By the way I have won some of those gong matches with a random fire form load, powder thrown, and junk bullets I never tune with before.... Oh ya, all my guns shoot zeros. I only shoot one shot. ;D